Colin said: "I think stammering is it's own issue, getting tongue tied or forgetting your words on stage or at a public speaking event, those are mortifying but they're not the same as stammering."

He went on: "But you can still draw from the blind terror that goes with that moment. I think anybody who appears in public life, whether it's on live television or they're politicians or actors speaking at events or whether we're appearing on stage, it's a constant anxiety."

The Bridget Jones star revealed he had to do a lot of preparation for the role, despite it being the third time he has played someone with a stammer.

He said: "What was interesting to me was you don't just pull out your stammer from your last performance.

"It's not going to be the same for everybody, it won't feel the same.

"And really what you're playing is not stammering. That is what you have got to arrive at because that's what the person is going through."